Generally, washing machines are classified into pulsator type washing machines which wash laundry using water motion generated by rotating a plate-shaped pulsator, and drum type washing machines which wash the laundry using falling of water and the laundry and frictional force therebetween generated within a horizontally laid tub by rotating the tub.
Among these washing machines, the drum type washing machine has been increasingly demanded in recent years due to its merits over the pulsator type washing machine in that the drum type washing machine uses a smaller amount of water and detergent, and is substantially free from damage and entanglement of the laundry when washing the laundry.
Generally, the construction of the drum type washing machine can be divided into a tub supported by dampers and springs within a cabinet, a cylindrical drum rotatably mounted in the tub, and a driving unit connected with the drum via a shaft to rotate the drum.
The cabinet is provided at a front side thereof with a door corresponding to an opening of the drum, a gasket between the door and the drum to maintain sealing of the drum, and a controller positioned above the door to control operation of the washing machine according to commands input by a user.
Meanwhile, a balance weight is mounted to either side of the front surface of the tub by means of a plurality of fastening ribs formed on the tub, and prevents vibration of the driving unit caused by unbalance of laundry contained within the drum using center of gravity of the balance weight.
For the drum type washing machine constructed as described above, rotational force of a rotor is transmitted to the drum via the shaft, and rotates the drum so that the laundry is lifted by baffles, and then dropped by gravity, thereby performing washing operation.
However, there is a problem in that the fastening bosses serving to mount the balance weights to the tub are damaged due to concentration of vibration from the tub and loads from the balance weights on the respective bosses when the drum rotates at high speeds.